Will it Fit?

A Comparison of Asymmetric Magnetic Reconnection Models

and Observations

Drake RanquistBrigham Young University

Advisors: Mari Paz Miralles and Nick Murphy2012 SAO Solar REU

Magnetic ReconnectionOccurs in highly conducting

plasmas when magnetic fields are oriented in opposite directions

Observed in Plasma Experiments, Earth’s Magnetosphere, and the Sun’s Corona

Responsible for energy release and topology changes during solar eruptions

Solar Flares and CMEsThe standard model of solar

eruptions includes:Rising plasmoid contained

by flux ropesX-line and current sheet

where magnetic reconnection occurs

Inflow and outflow at X-lineHot, bright post-flare loops

Locations where loops meet the photosphere are called footpoints

NIMROD CodeStands for “Non-Ideal Magnetohydrodynamics with

Rotation and Other Doohickies”

Magnetohydrodynamics (MHD) describes macroscopic behavior of conducting fluids like plasmas using Maxwell’s equations and standard fluid hydrodynamics

Solutions represented as sums of finite element basis functions

Includes resistivity and anisotropic thermal conduction

Conducting wall boundary conditions that represent the photosphere

Symmetrical Simulation

Asymmetrical Simulation

Observational Signatures of Asymmetric Reconnection

Distortion of post-flare loops

Asymmetric footpoint motions and brightness

Location of X-line and flow stagnation point

Different inflow velocities

Drifting of the CME current sheet

Circulation within the rising flux rope

QuestionsCan we find evidence of asymmetric

reconnection in observations?

How well do the post-flare loops from the simulations agree with the observations?

Can we determine the ratio of magnetic field strengths on the two sides of an observed post-flare loop?

Projection Effects:Symmetrical

Projection Effects:Asymmetrical

Observations: Two Events6/7 Dec 2010 and 7 Mar 2011

Primary Instruments:Atmospheric Imaging Assembly (AIA) on the Solar

Dynamics Observatory (SDO)SECCHI EUVI on STEREO-A and STEREO-B

Both events have a candle-like cusp at shorter wavelengths

6/7 Dec 2010

7 Mar 2011

Tracing LoopsChoose loop to fit and trace it by clicking mouse

and saving X and Y coordinates

Matching SimulationsWe assumed that the footpoints of the trace and

the simulation had to be at the same locationMagnetic field lines tied to solar surface Important to know exact location of footpointsCan automatically scale, center, and rotate

simulation about the Z axis

Only free parameters are:Rotation about the baselineLoop heightMagnetic field asymmetry

2010 Event

Symmetric Case Asymmetric Case

2011 Event

Symmetric Case Asymmetric Case

Results (AIA Only)Event 2010

12 loops traced8 loops match

simulations8:1 – 5 loops4:1 – 2 loops2:1 – 1 loop

Event 20117 loops traced6 loops match

simulations4:1 – 3 loops2:1 – 1 loop1.5:1 – 1 loop1.25:1 – 1 loop

These are the best fits in the AIA data, but not the only possible fits. Rotation into STEREO further constrained

results.

Rotation To Stereo

ProblemsSimulations are Two Dimensional

Doesn’t allow for more complicated 3-D structure

Simulated loops are isolated

Difficult to trace loopsThey split, merge, and twist

Footpoints often saturated giving greater error to location

ConclusionsThe simulations are able to fit most observations

This technique can be used to get a rough estimate on magnetic field asymmetries

The 6/7 Dec 2010 event is consistent with a magnetic field asymmetry of 4:1

The 7 Mar 2011 event is consistent with a magnetic field asymmetry of around 1.5:1

Future WorkUse same process for other events

See if HMI Magnetograms and potential field models indicate similar asymmetries

Determine error on tracing loops (especially with the footpoint locations)

Look for other observational signatures of asymmetrical reconnection and compare them to these results.

AcknowledgementsAdvisors Mari Paz Miralles and Nick Murphy

Harvard-Smithsonian Solar REU Program

NSF Grant that supports the REU ProgramATM-0851866

Ed DeLuca, Kathy Reeves, EMS crew, Hospital Staff, my Parents, and everyone else that kept me alive

Loop Unable to Fit (Kink)

HMI Magnetograms6 Dec 2010 7 Mar 2011